Last year i bought a running 2000 chevy blazer lt 4wd 4.3/auto, 150k, mint body and interior. i knew the engine didnt have long, as it smelled like coolant when running. there were no leaks and no white smoke. we got 6 months out of it before it blew the headgasket or a passage and locked the engine up when all the coolant dumped into the engine.

i pulled the dead engine and found a good running condition 4.3 v6 out of a 98-99 S10, with 115k and a year warranty.
i stuck it in last weekend, i have everything mechanical and electrical hooked back up now. its filled with fluids. ready go i think except. i have a mystery plug, its 2 prong female and comes out of the harness between the fuel delivery and throttle body on top of the engine, i think the rubber jacket on it is blue or black. anyone know where it goes?

i have a few other questions about these suvs too.

Is it ok to prime the oil system by tuning the motor over by hand, or by cranking the starter with no coil connection and pulling the fuel fuses?
Do these suvs have any issues with passlock after replacing the engine with a matching oem vortec v6 engine?
Anything im missing when it comes to these suvs and staring after a replacement engine?

 

A picture would help on the plug, but check and make sure you have a plug in the oil pressure fuel cutoff unit. Rear of the engine, right behind the lower intake on the drivers side. There is a metal adapter that screws into the block and the unit is screwed in at a 90 degree angle. It could be kind of hidden beneath the distributor.

I've never heard of anyone being able to prime the engine by turning it over by hand. When you use a drill motor and oil prime adapter, it turns quite a bit (couple minutes even) before oil reaches your rocker arms. I have heard of people turning the engine by cranking the starter. But in my opinion your not doing much more to prime the engine then actually starting it would. You still have non-lubed parts rubbing against each other creating friction until the oil gets where it needs to go. Just my opinion. Though if I had the distributor already installed as it sounds like you do...admittedly I myself would be very tempted to prime by cranking the starter.

 

It could be your coolant temp sensor located on the drivers side cylinder head

 

thanks for the places to check, ill grab some pics soon.

 

heres the plug.

i have the one under the distributer plugged i